<wicket:panel xmlns:wicket="http://www.w3.org/1999/xhtml">
  <div class="input-group date">
    <input type='text' wicket:id='date' class='form-control'/>
    <div class="input-group-addon">
      <i class="fa fa-calendar"></i>
    </div>
  </div>
</wicket:panel>